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% @(#)umsparutil.tex	1.1 95/10/24 
%
% Joachim Schimpf
%

\section{Parallel Utilities}
\label{chapparutil}

This library contains parallel versions of common sequential predicates.
It is loaded using
\begin{quote}
\begin{verbatim}
:- lib(par_util).
\end{verbatim}
\end{quote}
and it currently contains the following predicates:

\begin{description}
\item[par_member(?Element, +List)]
\index{par_member/2}
Parallel version of \bipref{member/2}{../bips/lib/lists/member-2.html}, i.e.\ selects elements from the
given list in parallel. Note that it cannot work backwards and generate
lists like \bipref{member/2}{../bips/lib/lists/member-2.html} can, the list must be a proper list.

\item[par_delete(?Element, ?List, ?Rest)]
\index{par_delete/3}
Parallel version of \bipref{delete/3}{../bips/lib/lists/delete-3.html}.

\item[par_between(+From, +To, ?I)]
\index{par_between/3}
Parallel version of \bipref{between/3}{../bips/lib/util/between-3.html}. Generates integers between {\it From} and
{\it To} in parallel. See also \bipref{fork/2}{../bips/kernel/control/fork-2.html}, on which it is based.

\item[par_maplist(+Pred, +In, ?Out)]
\index{par_maplist/3}
Parallel version of \bipref{maplist/3}{../bips/lib/apply_macros/maplist-3.html}.
The semantics is not exactly the same as \bipref{maplist/3}{../bips/lib/apply_macros/maplist-3.html}: It does not work
backwards and it does not cope with aliasing between the {\it In} and
the {\it Out} list, since it is implemented on top of \bipref{findall/3}{../bips/kernel/allsols/findall-3.html}.
There will only be a performance gain if the mapping predicate does
enough computation to make the overhead pay off.

\item[Goal1 \& Goal2]
\index{\&/2}
Parallel AND operator implemented on top of OR-parallelism.
This will only pay off for sufficiently coarse-grained
computations in {\it Goal1} and {\it Goal2}.

\end{description}

